1. Field of the Invention
The present application generally relates to a field effect transistor (FET), and more particularly to an FET with a depolarization layer.
2. Description of Related Art
Recently, III-V material such as gallium nitride (GaN) develops rapidly in the field of the high power devices because it has the piezoelectric effect to generate the two-dimensional electron gas (2DEG) at the junction where the electron mobility and the concentration are very high and the sheet resistance is low. Therefore, it has advantages of high current-density output, low switching loss and high voltage operation.
The operation modes of the GaN-based EFTs comprise normally-on mode (depletion mode) and normally-off mode (enhancement mode), wherein the normally-off GaN-based EFEs are generally E-mode FETs. However, the threshold voltage of the GaN-based E-mode FETs is still lower and may not meet the needs of commercial product application specifications